Various articles, e.g. tapes, films, ostomy and incontinence products and wound dressings, employ pressure sensitive adhesives which serve to hold the article in intimate contact with a fluid emitting area such as a wound. In many instances, the adhesive is used directly on the wound as well as on the surrounding normal skin. This requires that the adhesive be formulated from materials that can interact with the fluid emitted from the wound while forming a fluid-tight bond with the surrounding normal skin.
Such adhesives may typically include one or more natural or synthetic viscous or elastomeric substances, one or more water dispersible hydrocolloidal materials, and optionally a tackifier, a solvent or plasticizer and one or more water swellable cohesive strengthening agents.
For example, Chen et al. in U.S. Pat. No. 4,253,460, disclose an ostomy adhesive comprising a hydrocolloid gum, such as guar gum, locust bean gum, pectin, gum karaya and mixtures thereof; a pressure sensitive adhesive, such as natural rubber, silicone rubber, polyisobutylenes and the like; and, a cohesive strengthening agent, such as an inert natural or synthetic fibrous material, finely divided cellulose, a cross-linked dextran, a cross-linked carboxymethylcellulose, or a starch-acrylonitrile graft polymer. The cohesive strengthening agent provides that the adhesive is suitable for holding an ostomy product on the skin for an extended period of time, e.g. for a week or more.
Pawelcaak et al. in U.S. Pat. No. 4,538,603 disclose an occlusive dressing comprising a first adhesive layer which contacts the skin and wound, a semi-open cell elastic foam layer, and a film overlying said foam layer. A second more aggressive adhesive layer is interposed said first adhesive and foam to more suitably accommodate the difference in the adhesive requirements for the skin and the foam. This structure, based on a fluid-interactive adhesive, provides an excellent wound dressing which has enjoyed much commercial success in that the integrity of the structure is enhanced by the presence of the second adhesive.
By interaction of the adhesive with the emitted fluids is meant that a considerable portion of the fluids must be able to permeate through, or be absorbed into, the adhesive while the adhesive still maintains enough "wet tack" to adhere to the wound and the surrounding normal skin. As the adhesive interacts with large amount of fluids (extended time and/or heavy fluid flow), it typically becomes gel-like. Even though the designed-in "wet tack" properties maintain contact between the wound and the adhesive, the tenacity of the bond at the wound dressing/adhesive interface can be adversely affected.
Thus, since such fluid interactive materials adhere to the wound for extended periods, in many cases it is ultimately the loss of adhesion to the ostomy product, wound dressing, tape or film that necessitates replacement thereof. For example, even in the occlusive dressing of U.S. Pat. No. 4,538,603, described above, the fluids which eventually permeate the first adhesive are believed to have a deleterious effect on the second adhesive. Often it is the resulting separation of the semi-open cell foam and polyurethane film from the adhesives, and not slippage of the adhesives from the skin or wound, that makes a dressing change necessary. This is especially true for wounds emitting large amounts of fluids.
Also useful in the area of wound dressings are the calcium alginate fiber or wool dressings available as Kaltostat from Cair, Ltd. or Sorbsan from NI Medical, Ltd, known for their hemostatic capabilities. The calcium alginate wool is applied to a wound and begins to absorb wound fluids. Then, by ion exchange of some of the calcium in the wool with the sodium in the wound fluid, the dressing is rendered capable of absorbing yet larger amounts of fluid during which time the dressing takes on a gel-like consistency. The moist gel of the dressing is believed to enhance the healing process and facilitates less injurious dressing changes. A problem with these dressings, however, has been that they are air permeable and the gel can dry out and form a scab on the wound. Although these calcium alginate wools are completely biocompatible and biodegradable, the formation of the scab is thought to have a negative effect in the wound healing process. Since these wools form such a gel upon fluid absorption, adhesion of moisture impervious films thereto for the formation of occlusive dressings has proven a difficult task.
While the above-described articles and the adhesives they utilize continue to be extremely beneficial to the patient and clinician in the surgical, wound dressing, incontinence and ostomy care fields, products with an improved adhesive, particularly wound dressings, suited for use on wounds emitting large amounts of fluid would be a useful addition to the art.